Apparatus for making a two color rubber sale by injection molding and applying uniting pressure

ABSTRACT

An article of footwear having a two-color rubber sole construction, and a method and apparatus for manufacturing the article. The sole construction includes a midsole-foxing component having foxing surrounding and engaging an outsole component which is vulcanized to the midsole-foxing component. The rubber used for the midsole-foxing component has a higher modulus than the rubber used for the outsole component. The higher modulus rubber is injected into a mold cavity having a colume considerably greater than the volume of the injected rubber, and a movable sole plate spreads the injected rubber against the underside of a lasted upper. The sole plate has a peripheral shoulder which determines the lower end and inner surface of the foxing. The lower modulus rubber is also injected into a mold cavity of considerably greater volume. The sole plate is again advanced toward the lasted upper to spread the outsole rubber against the midsole rubber to be vulcanized thereto.

United States Patent 1 Borisuck et al.

APPARATUS FOR MAKING A TWO COLOR RUBBER SOLE BY INJECTIQNHMOLQVIVIYG ANDAPPLYING umrmc PRESSURE lnventors: John F. Borisuck, Ruben A. LaChall,

, both of Naugatuek, Conn. 1

Assignee: Uniroyal, Inc., New York, NY.

Filed: Aug. 5, 1970 Appl. No.: 61,457

US. Cl 425/119, 425/120, 425/129, B29h/7/08 Int. Cl B291 1/12, 32% 3/14Field of Search 425/119, 120, 129, 425/130, 125, 127, 242, 352, 416;264/244, 255

References Cited UNITED STATES PATENTS 2/1967 Ludwig 425/119 4/1968Wilcox 425/119 3/1968 Ludwig 425/119 2/1967 Ludwig 425/119 X Aug. 7,1973 Primary Examiner-J. Spencer Overhol'ser Assistant Examiner-David S.Safran Attorney-Henry Sternberg ABSTRACT An article of footwear having atwo-color rubber sole construction, and a method and apparatus formanul'aeturing the article. The sole construction includes amidsole-foxing component having foxing surrounding and engaging anoutsole component which is vulcanized to the midsole-foxing component.The rubber used for the midsole-loxing component has a higher modulusthan the rubber used for the outsole component. The higher modulusrubber is injected into a mold cavity having a colume considerablygreater than the volume of the injected rubber, and a movable sole platespreads the injected rubber against the underside of a lasted upper. Thesole plate has a peripheral shoulder which determines the lower end andinner surface of the foxing. The lower modulus rubber-is also injectedinto a mold cavity of considerably greater volume. The sole plate isagain advanced toward the lasted upper to spread the outsole rubberagainst the midsole rubber to be vulcanized thereto.

7 Claims, 9 Drawing Figures PAIENIED AUG 7 75 SHEH 1 BF 4 APPARATUS FORMAKING A TWO COLOR RUBBER SALE BY INJECTION MOLDING AND APPLYING UNITINGPRESSURE BACKGROUND OF THE INVENTION This is division of applicationSer. No. 729,570, filed May 16,1968. 1 i

The present invention relates to footwear.

In particular, the present invention relates to rubbersoled footwear andespecially to footwear having a twocolor rubber sole construction.

It is known to provide footwear having two-color sole structures made upof various plastic materials. While it is indeed highly desirable to userubber in such a sole construction, up to the present time it has notbeen possible to manufacture footwear successfully with a twocolorrubber sole construction using only injection or injection-compressionmeans. When using other plastic compositions, the latter are easilyinjected into mold cavities, whose configurations conform to the desiredmidsole or outsole, vso as to completely fill and set in these cavities.However, when using rubber, it is difficult to inject the rubber into amold cavity the size of which corresponds to the required size of themidsole or outsole because of the extremely high pressure required to beused in connection with rubber injection.

Furthermore, in a two-color rubber sole construction, difficulties areencountered in that during injection of the outsole there is a tendencyon the part of the latter to stretch and displace the midsole, even ifthe midsole is fully cured, causing undesirable rippling of the midsole.In addition, difficul'ties are encountered in achieving a sharp,well-defined boundary between the foxing and the outsole, because thematerial of the foxing undesirably mixes with that of the outsole. Inaddition, where a pair of injection ports are provided for the rubbermaterials which are respectively injected for the midsole and outsole,the initially injected material for the midsole unavoidably reaches theport for the outsole material, spewing into the latter and clogging thislatter port, so that difficulties were encountered during injection ofthe material for the outsole.

Thus, even though rubber is highly desirable because of its resiliency,traction, and comfort, nevertheless it has not heretofore been possibleto provide a completely satisfactory and practical method for makingtwo-color rubber sole construction for footwear. By the term two-color"as used herein, there is meant a pair of rubber materials of differentelastic modulus.

SUMMARY OF THE INVENTION It is accordingly a primary object of thepresent invention to provide a solution to the above problems.

Thus, it is an object of the invention to provide not only an article offootwear having a two-color rubber sole construction, but also toprovide a method and apparatus for efficiently manufacturing thisarticle.

Another object of the invention is to provide a method and apparatuswhich will make it possible to avoid the problems of undesirablestretching, rolling and rippling of the midsole component when theoutsole material is pressed against the midsole.

Also, it is an object of the invention to provide a method and apparatuswhich is capable of achieving a clean, sharply defined junction betweenthe outsole and the surrounding foxing.

Furthermore, it is an object of the invention to provide an article offootwear in which a midsole-foxing component is capable of protecting anoutsole component, particularly at the periphery thereof, while at thesame time excellent traction can be achieved with the rubber outsolecomponent.

In addition, it is an object of the invention, to provide an article offootwear which will protect against bruising when stones or pebbles arestepped on.

According to the invention rubber of given modulus is injected in aprecisely measured quantity into a heated mold cavity which has a volumesubstantially greater than the volume of the injected quantity ofrubber, and this injected rubber is received on a sole plate which,after the injection, is advanced toward a lasted upper to spread theinjected rubber against the upper to form a midsole which, through theapplication of heat to the mold, is vulcanized to the upper. Theconfiguration of the mold is such that simultaneously with forming ofthe midsole a foxing is formed integrally with the midsole and has aportion which projects downwardly therefrom.

The sole plate is retracted and rubber of lower modulus than said givenmodulus is then injected in a precisely measured quantity which is alsosubstantially less than the volume of the cavity into which it isinjected. After this second injection the sole plate is again advancedtoward the lasted upper so as to spread the lower modulus rubber againstthe higher modulus rubber midsole surrounded by the foxing, so as toachieve in this way an outsole component surrounded by and pressingagainst the foxing. The sole plate is retracted after the firstinjection when the rubber of the first injection has set sufficiently toprovide a clean retraction of the sole plate without any sticking of thefirstinjected material thereto, but before the first-injected rubber hasbecome fully cured, so that when the second-injected rubber is pressedagainst the first injected rubber in the heated mold it will becomevulcanized thereto.

Because the second-injected rubber which forms the outsole is of a lowermodulus than the first-injected rubber, this first-injected rubber isstiffer than the second-injected rubber and it is not possible for thesecond-injected rubber to cause undesirable stretching, rolling, orother displacement of the first-injected rubber. The outsole is thusvulcanized to the midsolefoxing component without any rippling or otherundesirable conditions existing between the outsole and the midsole.

In the apparatus of the invention, the mold is defined by a pair of moldrings which surround the mold cavity and which have an inner surfaceextending upwardly to an elevation somewhat higher than the upper edgeof the final foxing, while the sole plate is provided along its upperedge with a peripheral shoulder defining a recess into which the foxingextends. This shoulder of the sole plate thus determines theconfiguration of the inner surface of the foxing which surrounds andengages the outsole component as well as the extent to which the foxingextends downwardly beyond the bottom surface of the midsole after thefirst injection.

With this construction and method it has been found that there is nointermixing of the outsole material with the foxing at theoutsole-foxing junction. Any intermixing which does occur, using theprocess of the present invention, is restricted to the lowermost portionof the downwardly depending foxing material and is therefore locatedbelow the plane at which trimming takes place. There is thus provided aclean, sharply defined junction line between the outsole and the foxing,so that it is possible to provide a two-color rubber sole structure in ahighly efficient manner with the method-and apparatus of the invention.In addition, because the outsole is surrounded by foxing of a highermodulus, the outsole is protected by the foxing. The softer outsolematerial provides a better traction for the footwear, and at the sametime the harder or stiffer midsole material protects the foot againstbruising when stepping upon stones, pebbles or the like.

BRIEF DESCRIPTION OF DRAWINGS The invention is illustrated by way ofexample in the accompanying drawings which form part of this applicationand in which:

FIG. 1 is a schematic representation of the method and apparatus of theinvention as shown in FIG. 1 at a time just prior to the firstinjection;

FIG. 2 shows the mold structure of FIG. 1, and components associatedtherewith, at the end of the first injection;

FIG. 3 is a partly sectionalplan view taken along line 33 of FIG. 2 inthe direction of the arrows and showing the interior of the mold withthe first-injected rubber resting on the sole plate;

FIG. 4 is a transverse sectional elevation taken along line 4--4 of FIG.3 in the direction of the arrows, and showing the arrangement of theinjection ports of the mold;

FIG. 5 is a schematic representation of the structure of FIG. 2subsequent to the first injection after the sole plate has been advancedtoward the lasted upper to spread the midsole-foxing component againstthe up- P FIG. 6 schematically represents the position which the partstake at that stage of the method where the second injection takes place,FIG. 6 showing the method and apparatus at the end of the secondinjection;

FIG. 7 is a schematic representation of the position which the partstake subsequent to that stage of the method which is illustrated in FIG.6, FIG. 7 showing how the outsole component is vulcanized to themidsole-foxing component;

FIG. 8 is a fragmentary sectional elevation, on an enlarged scale, ascompared to FIG. 7, taken in a vertical plane through the heel region ofthe mold where the injection ports are located and showing in detail thecondition of the injected material and features of the apparatus of theinvention; and

FIG. 9 is a schematic representation ofa rotary turntable and a pair ofinjection guns used in the manufacture of the footwear of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to the drawings, themold 10 of the invention includes a pair of side rings 12 (FIG. 3) whichcan be moved in a known way toward and away from each other. The rings12 are shown in FIG. 3 in their closed position where they engage eachother to surround the mold cavity. As is apparent from FIG. 4, the siderings 12 are formed at the heel region of the mold cavity with elongatedchannels having tapered outer ends and a rectangular configuration incross section so that when the rings 12 have the closed position shownin FIG. 3 and 4, the channels of the rings will come together to form apair of injection ports 14 and 16 which are of rectangular crosssection, being longer in the ver tical direction than in the horizontaldirection, while having conically shaped flaring ends to receive theconically shaped nozzle of the injection gun, as explained furtherbelow. The rings 12 are also formed next to their upper surfaces withinternal peripheral grooves, so that when the rings 12 are in the closedposition shown in the drawings, these internal peripheral grooves forman endless inner groove 18 of arcuate cross section to determine theexterior configuration of the upper portions of the foxing. The innerside surface 20 of the mold, defined by the closed rings 12 extendsstraight up to the lower edge of the groove 18 without any interruption,except for the injection ports 14 and 16.

A lasted upper 22 is introduced into the upper end of the mold cavity toclose the mold cavity with the material of the upper, such as canvas,engaging the upper edge of the groove 18 of the inner periphery of theclosed mold rings 12. In this way the top of the mold is closed by thelasted upper 22.

The mold further includes a sole plate 24 slidable along the inner sidesurface 20, formed by the closed side rings 12, toward and away from thelasted upper 22. The sole plate 24 has an upper surface 26 directedtoward the lasted upper 22. Along the periphery of the surface 26 thesole plate 24 is formed with a peripheral shoulder 28 having theconfiguration shown most clearly in FIG. 8. In this way, the shoulder 28defines with the inner side surface 20 of the mold cavity a rec'esssurrounding the upper surface 26 of the sole plate 24.

The sole plate 24 is advanced upwardly and retracted downwardly by anywell known structure such as the pneumatic assembly 30 illustrated inFIG. 1. This assembly 30 includes a cylinder 32 in which a piston 34reciprocates, this piston being fixed to a piston rod 36 which in turnis fixed to the underside of the sole plate 24. A known valve assembly38 is provided for introducing air under pressure to the top side of thepiston 34 for retracting the sole plate while air at the under side ofthe piston 34 can escape through a lower known valve 40. On the otherhand, air under pressure can be introduced through the valve 40 whileair escapes through the valve 38 in order to advance the sole plate 24upwardly toward the lasted upper 22. The valves 38 and 40 can beactuated as by way of switch structure 42 tripped by cam 44 (FIG. 1)carried by the barrel 46 of an injection gun assembly 48. Thus, forexample during retraction of the barrel 46 from the mold 10 after thefirst injection, the switch 42 will be tripped to cause the sole plate24 to rise, in a manner described in greater detail below.

The gun 48 has a conical discharge nozzle 50 capable of being receivedin the outer conical end of the injection port 14 for injecting theextrudate into the mold cavity, and the gun 48 can have any knownconstruction according to which material supplied to the hopper 52 isplaced in a flowable condition under pressure so as to be injected intothe mold cavity in the form of a ribbon of preferably rectangular crosssection issuing from the port 14. The pressure with which the extrudateis injected is of substantial magnitude as required for rubber.

The apparatus further includes a second gun 54 shown fragmentarily inFIGS. 6 and 7 and used to inject a second quantity of rubber, the nozzle56 of the second gun being situated at the elevation of the lowerinjection port 16. This second gun 54 may be identical with the gun 48shown in the FIG. 1.

The material which is injected by the first gun 48 is a higher modulusrubber whereas as the material injected by the second gun 54 is a lowermodulus rubber. As is well known to those skilled in the art, themodulus of the rubber is a measure of the elasticity thereof. Forexample, rubber which has a modulus of 325 at 300 percent requires aforce of 325 lbs. per square inch of cross section to stretch a 1 inchlength of the rubber to a length of 3 inches. Thus, the force requiredto stretch a given length of the rubber derived from the gun 48 througha given increment is greater than the force required to stretch the samelength of rubber derived from the gun 54 through the same increment, sothat the higher modulus rubber injected by the gun 48 is stiffer thanthe lower modulus rubber injected by the gun 54. The different rubbermaterials respectively injected by the guns 48 and 54 may also havedifferent pigmentation. Thus, the rubber injected from the gun 48 may bewhite, while that injected from the gun 54 may be tan.

The various portions of the mold are heated by any conventional meanssuch as for example by electrical heating elements 71 (FIG. 2) totemperatures required for vulcanizing the rubber materials injected intothe mold. As is well known by those skilled in the art temperaturesapproximately in the range of 200-500 F. are required. The most suitabletemperature within such range depending upon the length of dwell in themold, the specific polymers used, and the curing or vulcanizing systemsemployed.

Referring now to FIG. 1, the parts will initially have the positionshown in FIG. I where the sole plate 24 is retracted to its lowermostelevation shown in FIG. 1 and the mold rings 12 are closed with theupper opening of the mold closed by the lasted upper 22. With the partsin the position of FIG. I and with the injection port 14 axially alignedwith the nozzle 50, the barrel 46 of the gun 48 is advanced into theouter end of the port 14, and in a well known manner a predetermined,precisely measured quantity of rubber is injected through the port 14into the cavity defined by the mold rings, the lasted upper, and thesole plate.

As may be seen from FIG. 2, which shows the parts at the end of theinjection of a ribbon of the higher modulus rubber 58, the ribbon ofrubber has a substantially rectangular cross section. The force withwhich the rubber is injected is sufficiently great so that the rubberribbon will be projected all the way from the heel region, where theinjection port 14 is located, to the opposed toe region of the moldcavity, and then as the ribbon of rubber continues to flow ,into themold cavity it will be deposited on the horizontal upper surface 26 ofthe sole plate 24 in the form of a generally sinusoidally shaped ribbonas indicated in FIG. 3.

The retracting movement of thebarrel 46 trips the switch 42 so that thevalve 40 is actuated to introduce air under pressure while the airescapes throughthe valve 38, and thus the sole plate is raised from theposition of FIG. 2 into the position shown in FIG. 5. It is to be notedthat the volume of rubber injected is considerably less than the volumeof the mold cavity, as is clearly shown in FIG. 2. Therefore, thedifficulties encountered in injecting rubber into a cavity which remainsconstant and which is required to be fully filled out by the injectedrubber are avoided with the method and apparatus of the invention.

The sole plate 24 is pushed upwardly to the upper elevation shown inFIG. 5, and it will be noted that at this elevation the sole plateitself closes the lower port 16 so that it is not possible for anyinjected material to have access to the lower injection port 16 whichthus remains unclogged.

As was indicated above, the rubber extrudate 58 is injected at asubstantial pressure so as to be projected in the form of a ribbon allthe way along the length of the mold to the toe region thereof afterwhich the rubber ribbon becomes deposited horizontally in the mannershown in FIG. 3. To achieve this the rubber may, for example, beinjected at a hydraulic ram pressure on the order of 1,200 psi. The soleplate 24 is pressed upwardly to the position shown in FIG. 5 with apressure acting on the piston 34 which may be on the order of 150 psi,where this piston has a diameter of somewhat less than 8 inches. Thisforce with which the sole plate 24 is urged upwardly toward the lastedupper 22 is sufficient to spread the material 58 in the manner shown inFIG. 5 to form midsole 60 and foxing 62 integral therewith. Because ofthe relatively small crosssectional area of injection port 14 the rubbermaterial remaining therein is rapidly vulcanized and prevents the risingsole plate from pushing extrudate in the cavity out through the port 14.

The configuration of the midsole and integral foxing 62 is most clearlyapparent from FIG. 8. When the sole plate 24 is at the elevation shownin FIG. 5, which is its upper elevation, the shoulder 28 will determinethe configuration of the inner side surface and bottom edge of thefoxing lip 64 which projects downwardly from the midsole 60 at the outerperiphery thereof.

The time during which the heated sole plate 24 remains in engagementwith the extrudate 58, with the parts in the position shown in FIG. 5,is not sufficient to provide full curing of the rubber but at the sametime is great enough so that when the sole plate 24 is retracted to itslower elevation shown in FIG. 1 and 2, the surface of the sole platewill cleanly separate from the rubber midsole-foxing component withoutany tendency of the latter to cling to the sole plate.

With the sole plate 24 again at its lower elevation as shown in FIG. 6,the gun 54 is placed against the outer end of the lower injection port16 so as to inject a second ribbon this time of the lower modulus rubberwhich is injected with a force sufficient to cause the ribbon of rubberto project all the way across to the toe .of the mold cavity. The rubberribbon being deposited on the surface 26 of sole plate 24 in the samegenerally sinusoidally shaped ribbon form as was the case with theextrudate 58 shown in FIG. 3. In this case also a precisely measuredquantity of low modulus rubber is introduced in a known way from the gun54. The gun 54 is retracted after a period of approximately one secondsubsequent to the injection, and then the sole plate 24 is again raised.The cam at the barrel of the gun 54 trips the switch 42, but at thistime the sole plate will rise to an intermediate elevation shown in FIG.7 which is lower than but adjacent to the upper elevation. The

sole plate 24 is also shown at this intermediate elevation in FIG. 8.

in the described manner on the sole plate as shown in FIG. 6, is spreadby the rising sole plate 24 against the midsole component 60 into thearea surrounded by the depending lip 64 of the foxing 62. It will benoted that the extent to which the foxing lip 64 extends down wardlyfrom the midsole component 60 is greater than the difference between theupper elevation of the sole plate 24 shown in FIG. and the intermediateelevation thereof as shown in FIG. 7, or, in other words, the thicknessof the outsole component 68 is less than the width or vertical dimensionof the lip 64. Furthermore, it will be noted from FIG. 8 that the soleplate 24, when at its intermediate elevation to form the outsolecomponent 68, has the lower surface of shoulder 28 situated slightlyabove the region of the top of the port 16 so that the material in thelatter is cut off from the outsole component 68.

When the outsole component 68 has cured sufficiently to permit goodrelease of the sole plate 24 the latter is again retracted to its lowerelevation. The side rings 12 are separated from each other in a knownway so that the lasted upper with the sole structure of the inventionvulcanized thereto can be removed. The material which sets within thepost 16 is very simply moved therefrom, and the material which setswithin the port 14 is integral with and projects from the rear end ofthe foxing 62. This projecting part at the rear of the foxing can be cuttherefrom, and the lip 64 is trimmed at approximately the elevation ofthe exterior lower surface of the outsole component 68. Trimming of theexcess material thus results in 'a smooth, continuous and sharplydefined junction line between, for example, an outsole 68 of tanpigmentation and a white foxing 62.

According to the preferred embodiment of the invention and as isschematically indicated in FIG. 9, the articles of footwear can bemanufactured on a rotary turntable 70. The turntable 70 may, forexample, have ten stations uniformly distributed about its periphery atangular distances of 36 from each other with a mold assembly andactuating structure, as shown in FIG. 1, situated at each of thesestations. The injection gun 48 is shown in FIG. 9 at station 1 while thesecond injection gun 54 is shown in FIG. 9 at station 5. A completecycle, or in other words a complete revolution of the turntable 70requires 3 minutes or 180 seconds, and the time of dwell at each stationis therefore 18 seconds. Thus, in a known way at intervals of 18 secondsthe turntable 70 is turned through 36.

After the operations described above have been completed and thestructure has arrived at station 10, the mold rings are displaced apartfrom each other, and the sole plate is retracted so that the last 22 canbe raised, turned over, and the shoe stripped therefrom. Now a new upperis placed on the last, turned over and lowered into position. The siderings 12 are closed, the sole plate is in its lower, retracted position,and now the turntable displaces this structure, corresponding to thatillustrated in FIG. 1, to station 1 where the gun 48 is situated.

The barrel of the gun advances to the upper injection port 14 in aperiod of 1 second, it remains at the injection port for I second,injects the first i.e., higher modulus material for a period of 3seconds, remains at the upper injection port for 1 second, and is thenretracted in 1 second, so that this complete operation of injectionrequires 7 seconds. As was indicated above the material may be injectedat a pressure on the order of 1,200 psi. Immediately upon completion ofthe injection, during retraction of the gun barrel, the sole plate israised to the position indicated in the FIG. 5 and remains in' thisposition until this structure approaches station 5. The action of thepneumatic assembly 30 on the sole plate 24 to advance the latterupwardly is such as to move the sole plate rapidly toward the last 22until the extrudate on the sole plate contacts the lasted upper and thento mover the sole plate at a relatively slower rate while the latterpresses the extrudate against the lasted upper. As each new moldassembly advances from station 10 to station 1, the above operations arerepeated at stations 10 and 1.

It will be noted from FIG. 9 that after four increments of turningthrough 36 with the dwells of 18 seconds between station 1 and 5, 72seconds will have elapsed. From this period of 72 seconds the initial 7seconds connected with operation of gun 48 will be subtracted, toprovide a cure time of 65 seconds for the higher modulus rubber which isfirst injected to form the midsole-foxing component.

As the mold approaches station 5 a cam (not shown) trips the switch 42so as to retract the sole plate 24 to its lower elevation at which it issituated upon arrival at station 5, and now the above operationsdescribed in connection with the first gun 48 are repeated with thesecond gun S4 at station 5, so that at the latter station the injectionof the second color extrudate,i.e., of the lower modulus rubber, alsorequires 7 seconds.

When the barrel of the second gun 54 is retracted the switch whichcontrols the movement of the sole plate is again tripped so that thesole plate is raised into the position indicated in FIG. 7, and now theassembly remains in this position through all of the several stations6-9 until the station 10 is reached, where the operations describedabove in connection with removal of the work at the station 10 takesplace. In advancing from station 5 to station 10, there are fiveincrements of turning of 36 each with dwell periods of 18 seconds inbetween, so that the total time required for the work to. reach station10 after leaving station 5 is seconds, from which the 7 seconds requiredfor operation of the second gun are subtracted to provide a curing timefor the second extrudate of 83 seconds.

Thus, with this construction it is possible for an operator at station10 to remove a shoe having the structure indicated in FIG. 8 every 18seconds so that the shoe can be further processed by having the foxingtrimmed at the elevation of the exterior surface of outsole 68 and byhaving the material previously located in injection port 14 removed. Ofcourse, within this period of IE seconds a new lasted upper isintroduced into the space which is surrounded by the side rings afterthe latter are closed.

It will be noted that with the method and apparatus of the invention, toprovide the above-described article of the invention, the first gun isretracted away from the mold in such a short time that it is notpossible for heat from the mold to vulcanize any of the rubber compoundat the gun nozzle itself. On the other hand, the rubber material locatedin each of the injection ports is, in view of the relatively smallcross-sectional size of these ports vulcanized at a sufficiently rapidrate which prevents any of the stock which is compressed by the soleplate from being extruded out through the port. It

is to be noted that at station the gun barrel is retracted within aperiod of 1 second after injection of the extrudate so as to preventcuring of rubber in the tip of the gun.

The vertical depth of the shoulder 28 is preferably on the order of25-30 percent greater than the thickness of the outsole component 68.

Of course, the external dimensions of the mold rings 12 are constant sothat they will fit the machine which moves them toward and away fromeach other. Therefore, when making relatively small shoes which requiresmaller cavities the horizontal wall thickness of the mold ringsincreases, thereby lengthening the injection ports. The increased lengthof these ports will normally require the cross-sectional area of theports to be altered accordingly so that the leading end of the ribbonextrudate will travel the required distance, without any impediment,toward the opposed toe region of the mold. Because of the particularconfiguration of themold and the presence of the lasted upper in itsproper position at the upper end of the mold cavity, the upper injectionport 14 may be slightly inclined in a direction leading downwardly intothe mold cavity while the lower injection port 16 is horizontal. I

' As a result of providing the sole plate itself with the shoulder 28which defines with the mold rings the recess of forming the foxing lipor rim64, the inner side surface 20 of the mold rings extends verticallyall the way up to the bottom edge of the groove 18. It is thisconstruction which with the shoulder 28 along the periphery of the soleplate enables the lip 64 of foxing 62 to be formed in such a way thatwhen the outsole component 68 is formed it will not intermix with thelip 64 nor with any flash which may have been formed during the formingof the foxing 62. A sharp clear line of demarcation is provided betweenthe two-color rubber sole components. The trimming is easily carried outwith a clean cutting away of the excess material being easily achieved.To facilitate the foregoing the vertical surface of shoulder 28 may havea slight draft of the order of 2. Moreover, the surrounding of the lowermodulus outsole component 68 by the foxing protects the softer outsolecomponent while at the same time the stiffer component 60 protects thefoot against bruising if the outsole component should engage pebbles,stones, or the like. In addition, the use of a lower modulus outsolecomponent 68 enables the shoe of the invention to achieve a bettertraction.

By way of example, the rubber materials used for the midsole-forcingcomponent and for the outsole component may be as follows:

' Parts by Weight C D Zinc dimethyl di thio carbamate 10 (Methazate) .871.12 1.12 1.12 n-t-Butyl-2-bcnzothiazole sulfenamide (Delac NS) 1.081.08 1.08 Benzo Thiazyl disulfide (MBTS) 1.08 DipentamethylenethiuramTetrasulfide (Tetrone A) .30 .30 .30 .30 Zinc Oxide 1.00 l.00 1.00 1.00Sulfur (Crystex) 2.94 2.94 2.94 2.94 Modulus at 300% Elongation Pounds]square-inch ASTM Experience has shown that the modulus of thefirstinjected rubber shouldv be at least lbs. per square inch at 300percent elongation greater than the modulus of the second-injectedmaterial. Thismodulus differential will prevent creeping and wrinklingof the midsole by the outsole. Thus, if composition D of the above tableis used for the midsole, then any of the other compositions A, B, or Ccan be used for the outsole sincethe modulus 430 is more than 100greater than the modulus of any of the other compositions. Also, it ispossible to use compund C as a midsole together with compound A as theoutsole, since in this case also there is a sufficiently great modulusdifferential. However, compound B would be unsuited as a midsole for usewith compound A as an outsole, and compound C would not be suited foruse with compound B as an outsole because in each of these cases themodulus differential is less than 100. Under ideal conditions themidsole has the highest possible modulus and the outsole has the lowestpossible modulus. However, as the modulus increases the flow indexdecreases, so that a balance or compromise of the desirablecharacteristics must be provided. The modulus of the compounds can bechanged in various ways, as, by changing accelerators, by incorporatingsuitable resins, and by incorporating suitable fillers. Thus, the Hi-Silfiller of the above table will increase the modulus, while the 31-10Resin will reduce the modulus.

It will be understood that while in the above example an SBR compositionhas been chosen to illustrate the article of the present invention andthe method and apparatus used to make the same, chloroprene elastomerbased compounds as well as compounds based on butyl rubber, EPDM,natural rubber, and other compounds similar to the foregoing can be usedas well.

Similarly, the outsole-component and the midsole foxing component mayeach be of a different one of the afore listed or similar compositions.

It will further be understood that as a result of the method andapparatus of the present invention any flash 80, i.e. first injectedrubber material which may findits way between the inner mold surface 20and the outer peripheral surface of sole plate 24 during forming of thelip 64 of foxing 62, will be pressed outwardly against the mold surface20 by the second injected rubber when thelatter is pressed against themidsolefoxing component. Thus, any such flash of first injected materialwill not be in a position both as a result of its location and of suchoutward pressing, to intermix with the second injected material anywherein the region of the ultimate trim line.

.Having thus described our invention, what we claim upper;-a sole platesurrounded by and slidably engaging said mold rings in their closedposition; means coacting with said sole plate for moving the lattersequentially between a first position in which said cavity has a givenfirst volume, a second-position in which said cavity has a given secondvolume smaller than said first volume, a third position in which saidcavity has a given third volume larger than said given second .volume,and a fourth position in which said cavity has a given fourth volumesmaller than said given third volume but larger than said given secondvolume; first injection means associated with said side rings andcommunicating with said cavity for injecting into said cavity, when saidsole plate is in said first position thereof, a quantity of midsolerubber of substantially smaller volume than said first volume of saidcavity; and second injection means associated with said side rings andcommunicating with said cavity for injecting into said cavity, when saidsole plate is in said third position thereof, a quantity of outsolerubber of substantially smaller volume than that part of said cavitywhich is not occupied by said midsole whereby said moving means raisessaid sole plate from a lower to an upper elevation during application ofa rubber midsole to said lasted upper and after initially retractingsaid sole plate to a lower elevation raises the sole plate a second timeto an intermediate elevation lower than but adjacent to said upperelevation during application of an outsole to said midsole.

2. The combination of claim 1 wherein said injection means eachcomprises an injection port and both of said injection ports aresituated in said side rings at an elevation higher than said lowerelevation of said sole plate and said ports including an upper portsituated at an elevation higher than said upper elevation of said soleplate and a lower port beneath said upper port and closed by said soleplate when the latter is at said upper elevation thereof.

3. The apparatus of claim 1 wherein said sole plate is formed at itsupper surface which is directed toward said lasted upper with aperipheral shoulder which determines the configuration of inner andbottom end surfaces of a foxing integral with the midsole.

4. The combination of claim 3 and wherein said lower port is situated atleast in part below said pcripheral shoulder of said sole plate at saidintermediate clcvation thereof.

5. The combination of claim 3 and wherein the difference between saidupper and intermediate elevations is less than the depth of saidperipheral shoulder of said sole plate, so that at said intermediateelevation of said sole plate the foxing integral with said midsoleextends below the upper surface of said sole plate.

6. In an apparatus as recited in claim 3 wherein said sole plate has anouter peripheral surface portion surrounding said peripheral shoulderthereof and in sliding engagement with inwardly facing surface portionsof said mold rings whereby flash which may form during application ofthe midsole-foxing rubber to the lasted upper will form intermediatesaid mold ring and sole plate surfaces at the outermost regions of thebottom end surface of the foxing in position to be pressed against saidinwardly facing surfaces of said mold rings by the outsole rubber duringapplication of the outsole to the midsole whereby intermixing of theflash material with the outsole rubber in the region of the innersurface of the foxing is prevented.

7. The apparatus of claim l-wherein said sole plate is at the sameelevation when in said first and third positions thereof.

I! '0' i I 2: 3; UNITED sums PA'IENT omen CERTIFICATE 0F CORRECTIONPatent No. 3 75 OO mud August 7, 1973 Inventerh) JOHN F. BORISUCK et a1.

- 'It 1. certified that error appears in the ibove-identifled patent andthat laid Letter. Patent are hereby corrected u chm below:

I Column IO, line 66, delete the word "have" and insert therefor--hav1ng--.

Signed and sealed this 20th day of August 197 v (SEAL), Attest:

McCOY M. GIBSON, JR. c. MARSHALL DANN Attesting Officer Commissioner ofPatents

2. The combination of claim 1 wherein said injection means eachcomprises an injection port and both of said injection ports aresituated in said side rings at an elevation higher than said lowerelevation of said sole plate and said ports including an upper portsituated at an elevation higher than said upper elevation of said soleplate and a lower port beneath said upper port and closed by said soleplate when the latter is at said upper elevation thereof.
 3. Theapparatus of claim 1 wherein said sole plate is formed at its uppersurface which is directed toward said lasted upper with a peripheralshoulder which determines the configuration of inner and bottom endsurfaces of a foxing integral with the midsole.
 4. The combination ofclaim 3 and wherein said lower port is situated at least in part belowsaid peripheral shoulder of said sole plate at said intermediateelevation thereof.
 5. The combination of claim 3 and wherein thedifference between said upper and intermediate elevations is less thanthe depth of said peripheral shoulder of said sole plate, so that atsaid intermediate elevation of said sole plate the foxing integral withsaid midsole extends below the upper surface of said sole plate.
 6. Inan apparatus as recited in claim 3 wherein said sole plate has an outerperipheral surface portion surrounding said peripheral shoulder thereofand in sliding engagement with inwardly facing surface portions of saidmold rings whereby flash which may form during application of themidsole-foxing rubber to the lasted upper will form intermediate saidmold ring and sole plate surfaces at the outermost regions of the bottomend surface of the foxing in position to be pressed against saidinwardly facing surfaces of said mold rings by the outsole rubber duringappliCation of the outsole to the midsole whereby intermixing of theflash material with the outsole rubber in the region of the innersurface of the foxing is prevented.
 7. The apparatus of claim 1 whereinsaid sole plate is at the same elevation when in said first and thirdpositions thereof.